Automatic switching system applicable to telegraphy



H. L. LESIGNE 2,529,166

AUTOMATIC SWITCHING SYSTEM APPLICABLE TO TELEGRAPHY Nov. 7, 1950 11 Sheets-Sheet 1 Filed March 16, 1946 Fig. 1 a

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INVENTOR HENRI LOUIS LE'SIGNE Nov. 7, 1950 H. LESIGNE 2,529,166

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AUTOMATIC SWITCHING SYSTEM APPLICABLE TO TELEGRAPHY Filed March 16, 1946 11 Sheets-Sheet l0 CQM INE posrn ems 4 4 4 5 6 7 8 $10 156 e c 1 e Fi 9 b /N l/E/V 7 0E H. L. LESIGNE Nov. 7, 1950 AUTOMATIC SWITCHING SYSTEM APPLICABLE TO TELEGRAPHY ll Sheets-Sheet 11 Filed March 16, 1946 nwE/vra/e fls/ve/ 400/5 [ES/GIVE iITaEn Ey um NUQR N mam QN EFEEZ Patented Nov. 7, 1950 OFFICE AUTOMATIC SWITCHING SYSTEM APPLICABLE TO TELEGRAPHY Henri Louis Lesigne, Vanves, France Application March 16, 1946, Serial No. 654,845

In France March 31, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires March 31, 1963 1 Claim.

The present invention relates to automatic switching systems more particularly applicable to telegraphy.

It relates, especially, to that kind of automatic switching which is the subject of my application for An Automatic Switching System Applicable to Telephony, Ser. No. 617,379, filed September 19, 1945.

In telegraphic systems, the supervision relays arranged series or in shunt on the wires of the line are generally polarised permanent magnetic relays which present the inconvenience of being expensive and require delicate regulating.

Ehe present invention replaces these polarised permanent magnet relays by more economical and stable relays with a shunted magnetic field.

These relays have the quality of attracting their armature when the two coils are traversed by a current of the same sense. They fall back when the current are of an opposite sense. These relays are used in the equipment of telegraph stations in equipment known as 2. Connection Circuit and in the device known as a Recorder.

Furthermore, the call-relay employed in a non-polarised relay with a magnet or electro magnet which permits discrimination of the direction of current through the line, the control of the passage of current through that line, and operation only in a determined direction.

One of the functions of the recorder is also to discriminate between stations according to their category. In the first category no charge is effected, whereas in the second category, a charge must be made. The recorder then sends the signals necessary for determining that charge. These signals are sent either locally, if the calling station is connected to the local automatic switch, or over the line to the calling station, if this is connected to another auto-- matic switch. The signals sent locally to the recorder which prints the duration of the communication indicates: the number of the called station, whether the called station has been found free or occupied, or whether the calling station is connected to overfiow equipment, and to which overflow equipment the calling station is connected. If the calling station is not connected to the automatic switch of the calling station, impulses are sent over the line to a remote automatic switch appropriated to the station or" the calling subscriber. The number of the impulses sen-t varies aocording'as the station of the called subscriber has been found free or occupied, or the calling subscriber is connected .to overflow equipment. In the last .case, the number of impulses sent varies according as the overflow relates to the first, second or third figure, thereby indicating also to the printing recorder in which stage of selection the overflow has occurred.

The recorder also permits the sending of a characteristic signal if the required station is occupied.

The present invention also envisages the possibility of indicating to the recorder that an operation is to be effected in a stage of selection, or to pass on from that stage of selection without the necessity of effecting a translation of the figures received in the recorder.

Furthermore it permits the changing of the route of a communication when the directon which it should ordinarily take is occupied. Nevertheless, the change of route cannot take place for communications which come from certain directions.

The present invention also comprises a device called a -Discrim-i-nating Recorder, the purpose of which is to replace the recorder in automatic switches when there is little local traffic, and when the traific is in great measure shunted to another office. This device fulfils the same functions as the recorder in the establishment of local communications.

The invention permits the substitution, in an automatic switch, for a recorder (that is, a device which permits the reception and the 'retransmission of the figures received in transit without it being necessary that the selector or connector should be connected to an outgoing line), of a discriminating recorder, that is, a simpler device, placed in series or in shunt with the line, and which determines whether the communication is local or in transit. This change may be effected without alteration of the cables. The recorder and the discriminating recorder being mounted on interchangeable flanges.

The present invention also provides for a recorder for charged communications, the purpose of which is to receive the impulses which determine the called station, to search by means of one or two seekers, according to the importance of the office, for the number of the calling station, and to receive impulses indicating the development of the communication: for example, requcsted station free, requested station engaged, transmission to overflow equipment in a local automatic switch transmission to overflow equipment, whether at the first, second or third selection. It retransmits these impulses to a group of devices called a printing recorder. It controls the placing in position of various elements provided with wheels with 3 printing characters which form this group. It controls the printing, on a band of paper, of the calling and called numbers, or of the place at which overflow occurs and the time when the communication begins.

The task of the recorder for charged communications is, furthermore, to search for the calling stations by a testing circuit provided at each station or at each finder.

The present invention relates equally to a printing recorder which comprises a very restricted number of elements and which is controlled by the recorder of the charged 'communications and remains connected to the connection circuit during the whole duration of the communication.

The present invention affords the possibility of increasing the number of lines connected to an automatic switch without increasing the number of the figures which serve to eifect the selection. Several lines may be assigned to the same calling number, but the number of figures which may be thus assigned need not be diminished.

According to a particular feature of the invention, one and the same selection figure may serve for two successive stages without retransmission of that figure, since the numerical elements of the recorder which orient the selection elements may be used once or more.

In the second instance, the invention permits the orientation of a selector in a given direction by making use of different figures, these figures being able to control the different directions at the succeeding stage of selection.

These various features of the invention and also others will appear and be better understood by a perusal of the following description which relates to an application of the system and is given by way of example and .by reference to the drawings attached to the text.

Fig. 1 is a schematic arrangement of elements entering into communication in the case where a recorder and a call finder are employed.

Fig. 1a is an assembly diagram showing how Figures 2, 3, 4, 5, 6, '7, 8, fit with relation to each other.

Figs. 2, 3, 4a, 4b, a, and 5b, 6 and 7, are detailed complementary schematic drawings and are related according to the sketch of Fig. 1.

Fig. 2 represents a control box for a telegraph station.

Fig. 3 shows the two special relays at each station, the input of the line to the automatic switch, the equipment of the call finder, the equipment of the connection circuit with the finder of the connection circuit and the first selector and the equipment of the connector.

Figs. 4a, 4b, 5a, and 5b illustrate a recorder.

Fig. 6 illustrates a supply element operated by rectified current and allotted to each recorder. This element has been described in the previous patent of the applicant, mentioned above.

Figs. 7a and 7b show a recorder for charged communications.

' Fig. 8 illustrates a recorder for printing the duration of a communication.

Figures 9a and 9b show a discriminating recorder.

Fig. 10 illustrates the connection of control wires when a secondary connector is employed.

Figs. 11 and 12 illustrate a device for changing the route of a communication.

The group of elements which enter into the establishment of a communication as shown in Fig. 1, consists essentially of the control-box of a calling station P, of its line equipment (call and metering relay) R, starting relays G, the recorder A with the finder of the recorder XI, of a connection circuit B with the finder of the connection circuit X2, or of a connection circuit 13' with its finder X4.

The connection circuit B is exclusively appropriated to an element relating to a figure in the hundreds. It is metallically connected to a call finder X4 fitted to the element in question;

The group of elements entering into the establishment of a communication comprises furthermore:

A call finder DX I.

A first selector with its rotary switch X3.

The group of primary selectors X3 is connected to the group of record rs A by control wires CI;

A connector E with its rotary switch X5;

The group of selectors or connectors is connected to the group of recorders A by control wires C3 and C4.

The line equipment of the called station R.

A control box of the called station P.

A recorder for charged communications H with its finders: that of the recorder X'I, that of the printing recorder X8, and the finders of the calling station X9 and XI 0.

A printing recorder I with its finder XI I.

The illustrated installation is for three selections. For four selections there should be an additional selector. For six figures two further selectors etc., but for two figures there would be no first selector.

The function of the system is in its broad lines as follows:

The operator of the calling station pushes down a call button but does not disconnect the control box of the station. He thereby excites the line relay of the station which operates the starting relays, these in turn closing the starting circuit towards a free recorder. The recorder searches in its turn for a free connection circuit, then by means of the finder of the connection circuit for a free call finder on the bank on which the line of the calling station is located. Thus the recorder shunts the call finder over the line of the calling station. Whilst the operations of preselection of the calling subscriber are being effected, a recorder for charged communications searches for a recorder and is temporarily connected thereto. It then searches for a printing recorder which in its turn searches for the connection circuit with which the assembly of a recorder and a recorder for charged communications is connected. A stand-by current is then sent over a wire of the calling station. The reception of this current at the callin station effects: starting-up of the motor of the teleprinter, connection of the telegraph line with the teleprinter through the control box. The operator then releases the call button of the control box, and dials the number of the called station, which may consist of three figures, as follows:

The first figure is received in the recorder by the numerical element allotted to thousands. The first selector is oriented, by means of the control Wires on the corresponding network to the same position as the numerical element allotted to thousands, then it searches for a free connector in the group in question. The second and third figures are received by numerical elements respectively allotted to tens and units, and orient the connector on the called line.

The various selections are similarly received by '5. the recorder for charged communications, which orients electromagnets of the printing recorder these being provided with wheels and printing characters and which prints the number of the called station on a band of paper.

In the meantime, the recorder for charged communications has searched the calling line and is cognizant of the number of the caller by the azimuthal position of its hundreds and subscribers finders. It orients the electromagnets of the printing recorder which are provided with printing characters and prints the number of the calling station. If the called station is free, it is called up by transmission of current of positive polarity over one of the wires of the line.

Reception of positive current at the controlboX of the called station starts the motor of the teleprinter associated with that station, and connects the telegraph line with that teleprinter.

A characteristic signal is then transmitted by the recorder to the called station. Reception of this signal stops the transmission by the called station of the indicative signal or" that station which is sent out to the Calling station and received by the recorder also. The recorder then transmits the same characteristic signal to the calling station, and thereupon establishes a connection in the connection circuit, the two telegraph lines being by this means connected with each other.

The recorder for charged communications then records on the printing recorder the time when the communication begins.

Then the recorder and the recorder for charged communications are released, leaving the printing recorder connected to the connection circuit during the whole duration of the communication. Upon the release of the elements at the end of the communication, the printing recorder marks the time when the communication ends, and is thereupon released.

In the detailed description which follows the letter 1- preceding the number of a contact spring of a relay indicates the contact established by the spring when the relay is at rest (not excited) and the letter if the contact established by this spring when the relay is at work. In this specification, the same relay and its contacts may be designated in any one of three different manners, according to its being considered independently of its condition of energization or de-energization, or considered to be in an energized condition, or in a de-energized condition. The designation of the relay in the first case will include neither the letter i nor the letter T, but, in the latter two cases will include either the letter if or the letter T.

It may be assumed, for instance, that a station wants to reach another station, the number of which is 25681. Referring now to Fig. 2, the operator at the calling station presses down the call button P of the control-box of the station. C is the dial of the calling subscribers station.

The pressing down of this button places a positive polarity (a stand-by telegraphic) on wire I of the station and starts the relay of line A (Fig. 3) by means of the following connections:

(Fig. 2) the positive resistance of the battery, the working contact of button P which is kept locked, r22 and wire I.

(Fig. 3) the winding RC3 of relay A, the rectifier Ax operating in the same direction as the current, and ground.

Relay A attracts its armature and closes the circuit of the starting relay MI as follows:

Ground, tA2, the winding of MI and the battery.

Relay MI sets a distributor (not shownon the drawing) in operation, by means of the following connections:

Ground, MI2, rTI and point I.

The ground connection is cut off as soon as relay T is excited, by means of the following connections:

Ground, tMI2, the winding of relay T and the battery.

The entr into action of relay MI establishes a test circuit on the call finders which have access to the group of which the calling station is a part, as follows:

Ground, MI I, rMZI, the resistance T023, and the bank of the finder of the connection circuit explored by the brush T.

On the other hand, relay MC is grounded, and the following connections are established:

Ground, rM2 I, r026, the resistance, the winding oiMC2 and the battery.

Relay MC2 is common to all call finders of the same group. It prepares the operational circuit of relay MCI. Relay MCI is common to all connection circuits explored by the same recorder. The plug M which is common to all the connection circuits which have access by their finders to the call finders of a group in whicha subscriber is being called, is brought to positive polarity thereby indicating a free line by means of the followin connections:

Ground, tMCZI, the resistance, r2I', and plug M on the bank of recorders.

The traflic distributor, by means of connections:

Ground, tMCII and point 8, rotates automatically searching for a free recorder. Its brushes stop on the azimuthal position which corresponds to a free recorder.

Relay 9 of the recorder (Fig. 4) then enters into action by means of connections: Ground, MCI 2 (Fig. 3), point II'(Fig. 4), point 25, the coil in the traffic distributor which is not shown in the drawing, point 26, sector A of switch X5 in its rest position, sector A in restposition of switches XI, X2, X3 and X4, wire 62 (Fig. 5) sector C in rest position of switch X'I, contact G of the mixer X6 in position 0, wire 58 (Fig.4), the winding of relay 9 and the battery.

By means of contact t92, relay 9 is held independently of the trafiic distributor which had effected its attraction, as follows:

Ground, tMCIZ (Fig. 3), point II (Fig. 4) t92,

the rest position of numerical elements X5, XI, X2, X3 and X4, wires 62 (Fig. 5), sector C of X1 in its rest position, contact G of the mixer X6 in its rest position, wire 58 (Fig. 4), the winding of relay '9' and the battery. I

As long as the relay MIC (Fig. 3) is working, that is as long as the call continues which brings a connection circuit on the bank of a recorder into action, relay 9 is attracted (see Fig. 4). It returns to rest either because the recorder of which it forms part, establishes connection with the calling station, or because another recorder is connected to the calling station, and thus blocks the operation of the recorders.

Relay 9, when in operation, effects the excitation of relay I3 by means of the following connections:

Ground, t95, wire 42 (Fig. 5), contact C of mixer X6 in position I], the lower winding of relay I3 and thebattery.

Rotary switch E begins to rotate automatically and searches for a connection circuit in which plug M has positive polarity. Its rotation circuit is closed, as follows-z (Fig. 4), battery, t9I, wire 31 (Fig.5), 14I, tl34, contact A of mixer X6 in rest position, wire 35 (Fig. 4), H1, Hill, the interrupter, the winding of E and the battery.

The rotation circuit of switch E is opened, upon the closin of the blocking circuit, at the time when brush M passes-a contact corresponding to a connection circuit which has access-to the called group. Relay I4-is excited. by means of the following connections: I

(Fig. 3), ground, tMCZI, the resistance r2I, contact M brush M (Fig. 4), 1393, N02, TI I I, wire 4| (Fig. 5) ,contact C of mixer XI in position 0, the winding of relay I4 and the battery.

By means of contact HM, the rotation circuit of E is interrupted. On the establishment of contact tl4l, relay [4 connects the upper winding of relay I3 to the battery, wire 31 (Fig. 4), t9I and the battery. The other end of its winding is connected to wire M, and current flows through the two windings of relay I3. The relay I3, the two windings 6f which are arranged differentially, .falls back when the flux produced by the upper windin cancels the flux produced by the lower winding. This condition is fulfilled if none of the other relays I3 is connected to the same point On the other hand, the upper winding of the relay l3, which is a low resistance winding, shunts the winding of relay I4. The potential of test plug M consequently falls to a value near the potential of the negative'pole of the battery. The

connection circuit is thus protected against engagement by another recorder. Relay l3 at rest and relay I4 in operation characterise the engagement of anunoccupied element. I

In the opposite case, relay I4 falls back, these relaysbeing' designed in such a manner that two of the relays l4 a're notable to operate simultaneously, since each is shunted by the winding ofrelay I3.- 1

Excitation of relay I4 and de-excitation of relay I3" efiect theattraction of relay I6 as follows:--

The battery, resistance rI3I, H42, the winding of relay-Iii'andground,

By means ofthe following circuit: ground,

rI'II tI63,' contact D ;of mixer X6 in position 0, wire 43 (Fig. 4) and r-IBI, the energising circuit of relays I and I0 is closed, their lower windings being arranged in series. Relay I0, the attraction of which is delayed, will not yet have attracted its armature when the contacts of relay I0 are already established. By means of contact H02, the upper windings of relays I0 and I0 are connected in branch with point M. Relay IIlis held by its upper winding, but relay III, the windings of which are arranged differentially 5 cannot operate, and its armature is left at rest. But relays III and ID are connected by contact H02 in shunt to the group formed by relays I3 and I4. Relay I4-being shunted, relay l3 functions again, and opens the circuit of relay l6 which then falls back. The grounding of the lower windings of IO and Ill effected by contact tl63', is interrupted.- Relay I0 attracts its armature. 'The'two relays l0 and I0 are held in working position by means of the following connections: v V V The upp'er'iwindings of i0 and I 0 tl I12, r93, brush M, contact M (Fig.i. 3 rZI, resistance tMCZ'fandground. 1 l

The rotation circuit of the finder in the connection circuit is thus closed, as follows:

(Fig. 4), the battery, till, wire 31, (Fig. 5), TIM, tI34, contact A of mixer X6 in position 0, wire 35 (Fig. 4), 111, M03, 1'1I3, brush TI of the finder of the connection circuit, contact rl (Fig. 3), the interrupter, the winding of the electromagnet RCI and ground.

Rotary switch RCI participates in the search for a free finder which has access to the called line, on the passage of brush T over a free call finder characterised by the positiv battery on plug M. Relay I4 of the recorder (Fig. 5) is energised' by means of the following'connections:

(Fig. 5) the battery, the winding of relay I4, contact 6 of mixer X6 in position 0, wire 4|, (Fig. 4), H I I, H92, H54, r13, brush tl of the finder of the connection circuit, contact TI' (Fig. 3), the brush and bank T of the finder of the connection circuit r023, resistance TMZ I, tMII and ground.

Relay I4 of the recorder (Fig. 5), then comes into operation. By means of contact rI4I, it opens the rotation circuit of the finder of the connection circuit. Armature I4I of relay I4 shunts the upper winding of relay I3, which is a low resistance winding, across the winding of relay I4. The potential of the test plug consequently falls to a value near the potential of the negative pole of the battery. The call finder is thus protected against engagement by another connection circuit.

Relay I3, which is a differential relay, falls back, because the fluxes which its two windings produce balance each other exactly.

Relay I3 at rest and relay I4 in operation close the attraction circuit of the relay It by the following connections:

The battery, resistance, rI3I, H42, the Winding of relay I6 and ground.

They also close the attraction circuit of relay I I by the following connections:

Ground, rI'II, H63, contact D of mixer X6 in position 0, wire 43, tIlJl, rI I3, the lower windings of relays II and II and the battery.

. Relays II and II operate in the same way as relays I0 and I0. Relays I3 and I4 are shunted by the windings of relays I! and II. Relay I3 is again excited and opens the attraction circuit of relay I6 which therefore falls back. Relay II, the lower winding of which is isolated from ground by means of contact H63 then begins to operate under the influence of its upper winding. Relay 8 then functions by means of connections:

The battery, the two windings of relay 8 in series, tI I I, brush SI of the finder of the recorder, contact SI (Fig. 3), the brush and bank S of the finder of the connection circuit r024, the winding of relay C2 and ground.

Relay C2 cannot begin to operate, because the resistance of the two windings of relay 6 is too great to permit of its functioning. Relay 6 of the recorder therefore closes the rotation circuit of the call finder RC2 as follows:

(Fig, 4) the battery, t9I, wire 31 (Fig. 5), TIM, i134, contact A of mixer X6 in position 0, wire 35 (Fig.- 4), H1, H03, tI I2, t83, brush BI of the finder of the recorder, contact BI (Fig. 3),

the brush and bank B of the-finder of the con-' nection circuit, TC22, the. interrupter, the winding of RC2 and ground. l I

The call finder RC2 begins to rotate automatically when exploration of the calling line starts. This line is .bh'aracterised by apolarity which may be calleda" blocking polarity on con- 9 tact T of the bank of the call finder. Relay I4 of the recorder then functions by means of the following connections:

(Fig. the battery, the winding of relay l4, contact 6 of mixer X8 in position I wire 4| (Fig. 4), till, E82, 1213!, THE, brush A! of the finder of the recorder, contact Al (Fig. 3), the brush and bank A of the finder of the connection circuit, rCZl, brush T of the call finder, and contact T which corresponds to the called line T.

The rotation circuit of the call finder is opened by means of contact M41, and blade M! of relay I4 shunts the upper winding of relay 13, which is a low resistance, across the winding of relay [4. The potential of plug T of the calling lin consequently falls to a value near the potential of the negative pole of the battery. The called line is thus protected against engagement by another connection circuit.

Relay l3, which is a differential relay, falls back, because the flux produced by its two windings, balance exactly.

Relay H3 at rest and the relay [4 in operation close the attraction circuit of relay [6 via:

(Fig. 5) the battery, resistance rl3l, tl42, the winding of relay l6 and the battery.

The circuit of relay 3 of the recorder (Fig. 4) is then closed via:

Left hand coil, ground, t9l', the winding and the battery.

Right hand coil, the positive current, the resistance, tll4', wire (Fig. 5), H52, wire 44 (Fig. 4), t8l, the right hand winding and ground.

Relay 3 which is a relay with a shunted magnetic field, and the windings of which are traversed by current of any desired direction, comes into operation.

Operation of relay 3 eiTects attraction of relay 4 by means of the following connections:

(Fig. 4) ground, the lower winding of relay 4, t3l, the resistance wound on relay 5 and the battery.

Relay 4 closes a holding circuit by means of contact H4, and contact t42 establishes the circult of the left hand coil of relay 3, which is open at t9l as soon as relay 9 is released at the end of the preselection operation.

By means of contact $43, it excites relay 1, which connects the recorder of the calling line.

By means of contact 1519' (Fig. 4), relay 1 engages the connection circuit with wiper M. A battery in series with a resistance is connected to wire 1.! to hold the connection relays by means of contact t13. By means of contact t19, relay 1 short-cricuits the upper winding of relay 8. Relay 02 (Fig. 3) of the call finder, in series with relay 8, then begins to operate, and by means of its working contacts it establishes the connection of the calling station with the recorder by means of the following connections:

(Fig. 4) ground, the right hand winding of relay 3, H8, Wiper B of the finder of the recorder, contact B (Fig. 3), r21, the brush and bank B of the finder of the connection circuit 1:022 the brush and bank B of the call finder, wire B, point I (Fig. 2) r22, the working contact of button P, the resistance and positive pole.

Relay 3 of the reccrder (Fig. 4) is held in operation. Relay I 4 of the recorder having had its circuit open at 102i (Fig. 3) falls back, and at H42 (Fig. 5) it opens the attraction circuit of relay I6 which also falls back, thereby opening at H62 the attraction circuit of relay 3 which remains under the effective control of the call- 10 ing station, this being a station for chargedcommunications. Relay l of the recorder begins to operate by means of the following connections:

(Fig. 6) the secondary of transformer TFI, the rectifier RDI, RD2 in the same direction as the current, point 23 (Fig. 4) fl2', t92, rill", brush SI of the finder of the recorder, contact S2 (Fig. 3), brush 8 and bank S of the finder of the connection circuit tC24, the brush and bank S of the call finder, the resistance, point I), point l0 (Fig. 4), rl Hi, the lower winding of relay I, the rectifier rDl in the same direction as the current, 1794', 2212, point 24 (Fig. 6), either rectifier Rd3 or RM, and the secondary of the'transformer.

Relay I begins to operate and closes its holding current by means of the following connections:

Ground, til, the upper winding of relay I and the battery.

Thus relay l puts the recorder for charged communications (Fig. 7) into operation by means of thefollowing connections:

(Fig. 4) Ground, tl3, the resistance, point 422a (Fig. 7), r83, contact I) of the mixer XI in position I), the winding of relay 2 and the battery.

Relay 2 closes the circuit of the differential relay 3 which begins to operate by means of the following connections:

Ground, t2l, contact d of mixer XI in position 0, the lower winding of 3 and the battery.

The circuit of the switch RC is then closed as follows:

The battery, MI, 2533, t23, the the winding of CE and ground.

The switch CE participates in exploration of the recorder since it is in connection with a connection circuit which is itself in connection with the called line. This recorder is characterised by a positive polarity on its wire M (Fig. 4), ground, tll3, the resistance, and bank M. When the wiper M of the finder CE passes over the contact M which corresponds to this recorder, relay l4 of the recorder for charged communications begins to operate by means of the following connections:

(Fig. 7) the battery, 1532, tZZ, the brush M and bank of CE .(Fig. 4), the resistance, H3 and ground, and it closes a holding circuit by means of its element t43.

The rotation circuit of finder CE is open at 1'4! (Fig. 7). By its blade 4!, relay 4 places the upper winding of relay 3, which is of weak resistance in shunt with the winding of relay 4. The potential of the plug consequently falls to a value near the potential of the negative pole of the battery.

The recorder is thus protected against engagement by another recorder for charged communications.

Relay 3, which is a differential relay, then falls back, because the flux produced by its windings balance exactly.

contact-breaker,

Relay [0 (Fig. 7) then begins to operate by,

means of the following connections:

Ground, 1' 3!, M2, contact ,0. of mixer X] in position 0, the lower winding of It) and the battery, and it closes a holding circuit by means of tlM, the wiper and bank M of finderCE (Fig. 4) the resistance, H3 and ground.

Relay 8 then begins to operate by means of the following connections:

Ground, H02, the winding of '8 and the battery.

11 Thecircuit of theelectromagnet of mixer X! is closed as follows:

Ground, t24, contact cof mixer X in positiQnIJ, the winding of XI and the battery. Mixer' XI then attracts its armature.

v 0n the other hand, the attraction circuit of relay 2 is'opened atrBB, and relay 2 which has a release, overcomes its delay and falls back, thereby opening at 1524 the attraction circuit of switch X! which then releases its armature and brings-its brushes into position I.

Relay 3 operates under the action of its lower windingthe circuit of which is again closed as follows: 7

The battery, the lower winding of relay 3, contact d in position I of XI, W4 and ground.

Exploration for a printing recorder then begins, because the rotation circuit of finder RE! is closed as follows:

The battery, MI, r33, contact a in position I of XI, the circuit breaker, the winding of RE! and ground. I

Switch RE! participates in exploration for a free printing recorder. A free printing recorder is characterised (Fig. 8) by a ground connection on the contact T of the bank of the finder RE! as follows: 7

Ground, the winding in parallel of relay I, 12!, rIAI, and contact T.

When the wiper T of the finder RE! passes over the contact T which corresponds to a free printing recorder, relay 4 of the recorder for charged communications begins to operate by means of the following connections:

. The'battery, the winding of the relay 4, t32, contact b of mixer X! in position I, wiper T (Fig. 8), contact T, MM, 12!, the twowindings of relay and ground, and it closes a holding. circuit at 3.

The'rotation cicrcuit of switch RE! isopen atr II. g "1 By means of its blade 4! relay 4 places the up:

per winding of relay 3 (which is a winding'of small resistance), in shunt with the winding of relay 4. The potential of the test plug consequently falls to a value near the potential of the negative pole of the battery. I

The printing recorder is thus protected against engagement by another recorder for charged'communications. v 7

Relay 3, which is a differentialrelay, then falls back, because the flux produced by its windings is exactly balanced. I

' Relay 3 at rest and relay 4 in operation in posie tion I characterise the end of exploration for a free printing recorder. Mixer X! has its circuit closed as follows: 7 j

Ground, r3 I, 7:42, contact 0 of mixer X! in position I, the circuit-breaker, the winding of XI and the battery.

Mixer X! then brings its wipers into position 2. In this position exploration for' connection circuits in engagement with the calling line and the recorder is effected.

The rotation circuit for the finder'of the printing recorder is closed as follows:

(Fig. '7) the battery, M23, 1'! I I, tIUI, contact 0 of mixer X! in position 2, wiper R offinder CE. I contact R of the circuit-breaker bank, the winding Re and ground. 7

Switch RC participates in the search for a connection circuit in engagement with the recorder. The connection circuit is characterised in that its wire S has a common point with wire S of 3. 16

recorder. r

When wiper S of the finder of the printing recorder passes over the wire S which corresponds to a connection circuit associated with a recorder connected with the recorder for charged communications, and with which the printing recorder itself is momentarily associated, relay I I of the recorder for charged communications (Fig. '7) begins to operate by means of the following connections: J

(Fig. 6) the secondary of T.F.I, rectifier R.D .I. or R.D.2. in the same direction as the current, point 23 (Fig. 4) H2, r! I I, wiper S! of the finder of the recorder, contact S! (Fig. 3), contact S of the bank of the finder of the printing recorder,

I wiper S of RC (Fig. 8), contact S of the bank of t! I13, wiper S of the finder of recorder CE, contact S of the bank (Fig. 4) tIG, rectifier R.D.I. in the same direction as the current, t'I2, point 24 (Fig. 6), rectifier Rd4 in the same direction as the current, and the secondary of transformer T.F. I.

Relay II, at r! II opens the rotation circuit of the finder of the printing recorder RC which stops its wipers on the designated connection circuit.

The circuit of the crossing relay is then closed as follows:

Ground, tBI, 1.! I2, contact bof mixer X! in position 2, the winding of relay I2, the resistance and the battery. 7

The circuit of mixer XI is closed as follows:

Ground, H2 I, contact (1 of mixer X! in position 2, the circuit-breaker, the winding of XI and the battery.

Mixer X! then brings its brushes into position 3.

Since relay II has had its circuit open at 112 it falls back, and by means of contact tII2, it opens the circuit of relay I 2, which is held in operation notwithstanding its delay. In this position the circuit of the electromagnet which advances the band of the printing recorder is closed as follows:

(Fig. 7) ground, t84, contact a of mixer X! in position 3, wiper Ab of finder R.E.I, contact Ab (Fig. 8) relay I3 and the battery.

Relay I3 advances the band. At the same time, mixer XI having attracted its armature, itscircuit'of attraction is closed as follows: 7

Ground, tBI, tI22, contact c of mixer XI, the winding of the electromagnet XI and the battery.

Relay I2, the circuit of whichis closed via;

Ground, t8I, 7522, contact I) of mixer X! in position 3, the winding of relay I2, H22, 758! and. ground, exhausts its period of delay .and falls back, and at: H22 it opens the attraction circuit of electromagnet X! which thereupon releases its armature, and brings its wipers into position .4.

At this moment the operator of the calling station must be informed that he cancompose on his dial the number of the station which he wants to reach, say: 25881.

One of the wires of the line is then connected to the positive pole of the battery, due to the following connections: (Fig. '7) the positive terminal of the battery, the resistance, r5I, t8 5, wiper 'b of finder CE, contact I), (Fig. 4) t! I I, 182, TI, wire 30 (Fig. 5), 'r2IlI, rI'I2, Wire 3! (Fig. 4), brush A of the finder of the recorder, contact a (Fig. 3), the wiper and contact A of the finder of the con nection circuit, 2502!, the wiper and contact A of the call-finder, wire A, point 2 (Fig. 2) the re-. IWl959i I 1? Windingof relay I in series with.

13 the line, the winding of the telegraphic relay 3 in series and ground.

The polarised relay 3 reciprocates its armature which comes into contact with its positive stop.

Then the relay 2 begins to operate by means of the following connections:

The positive terminal of the battery, the resistance, the positive stop of relay 3,1'23, the winding of 2 and the battery.

Relay 2 closes a holding circuit by means of contact r2 I, the resistance and the positive terminal of the battery.

By means of its contact rZI, relay 2 closes the circuit of the left hand coil of relay I which has a shunted field. This relay, the two coils of which are traversed by current of the same direction, begins to operate, and at rII it opens the release circuit of relay 2. At 1522' and 1523, relay 6 connects the telegraphic circuit with the teleprinter across the junction-box. At 1523 and t24', relay 6 establishes a connection between the motor situated at points 5 and 6 and the supply source situated at points 3 and 4. The start of the motor of the teleprinter indicates to the operator that a recorder is connected to its line. He ceases to press down the call button of teleprinter P.

The operator then composes on the dial of the control-box the number of the called station.

RECEPTION The operator uses his dial to compose the first figure of the required station, i. e. the 2 in the before-mentioned example. During its return to rest the dial 0 (Fig. 2) sends out two pulses of double current over the Wire I. These pulses of double current strike relay 3 of the recorder (Fig. 4). Relay 3 is a relay with a shunted magnetic field which falls back at each emission of negative current. These pulses are sent by means of the following connections:

Negative current, the resistance, the left hand contact of the dial C (Fig. 2), 1622, Wire I (Fig. 3), contact B and wiper B of the call finder, tC22, contact B and wiper B of the finder of the connection circuit 12L contact BI of the bank of the finder of the recorder (Fig.4), wiper BI, H8, the right hand winding of relay 3 and ground.

The first release of relay 3 determines the start of the operation of relay 5 by means of the following connections:

Ground, r3I, M4, the Winding of relay 5, the resistance wound on relay 5 and the battery.

Relay 5 is short-circuited at each attraction of relay 3, but its delay is consequently greater than the duration of a closing impulse, so that relay 5 cannot fall back during the transmission of a train of pulses. It only falls back when the operator of the calling station uses his dial for transmission of the next figure.

The circuit of the electromagnet of the entrance distributor X5 is closed as follows:

Ground, t ll, t5I, sector of X5, the winding of X5 and the battery.

The electromagnet X5 attracts its armature and remains in this position till the release of relay 5 which takes place at the end of the reception of the train of pulses which represent the figure to be received, in this case the figure 2.

The circuit of the numerical element corresponding to tens of thousands is closed as follows:

Ground, MI, 732, wiper a of distributor X5 in position I, wire I, the winding of switch XI and the battery.

At each emission of negative current by the dial of the calling station, relay 3 is de-energize d.

This relay is, on the other hand, attracted at each emission of positive current.

The circuit of the numerical element XI is, therefore, established at each emission of negative current. It follows therefore that the numerical elementXl performs as many steps as there are unities in the retransmitted figure.

In the example chosen the numerical element XI makes two steps and brings its wipers into position 2.

Relay 5, which is .short-circuited for a long time, exhausts its period of delay and is deenergized, thereby opening at t5I the attraction circuit of the entrance distributor X5 which releases its armature .and brings its wipers into position 2; this disconnects the numerical element X2 corresponding to thousands.

The second figure is received by X2 in a manner identical to that described for the reception of the first figure.

The same applies to the third and fourth figures which are received by numerical elements X3 and X4. The entrance distributor X5 after having effected distribution of the four first figures to the numerical elements XIX2-X3-X4 brings its wipers into contact with sectors 17-dcg and i by means of the following connections:

Ground, positions 5-6-'I8-'9 and II) of sector a, the circuit breaker, the winding of XI and the battery.

In this position switch X5 receives the pulses which determine the unit figure by means of the following connections;

Ground, MI, 132, 252, the winding of X5 and the battery, and brings the wipers into a position determined by the number of the received impulses (in the example chosen, the figure 1).

After transmission of the last figure the numerical elements of the recorder are in the following positions:

in position 2 in position 5 in position 3 in position 8 in position I At the end of the selection the operator of the calling station receives the signal of the required station if the latter has been found free, or the engaged signal if the latter is busy, or the indicativesignal of the overflow equipment.

On the other hand, the pulses received by the recorder must also be transmitted to the recorder for charged communications which causes the electromagnets of the printing recorder to take a position corresponding to the number of the desired station.

Relay 3 of the recorder (Fig. 4) re-transmits the impulses which it receives from the calling station via:

Ground, MI, 132, contact I of the bank of the finder CE (Fig. 7), wiper I, contact b of mixer XI in position 4, the winding of relay I3 and the battery. i

The first attraction of the relay I3 energizes relay I4 via: 1

Ground, tI3I, the inductive winding, the resistance wound on relay I4 and the battery.

Relay I4 closes the holding circuit as follows:

Ground, H42, its two windings in series and the battery.

Relay I4 is short-circuited each time relay I3 falls back, but its period of delay is greater than the period during which the circuit which receives the impulses is open, so that relay I4 cannot fall back during the transmission of the train of pulses. It falls back only when the operator of the calling station uses his dial to transmit the next figure, during which period the relay I3 is at rest and short-circuits relay I4 for a sufficiently long time.

The circuit of the electromagnet of mixer XI is closed via:

Ground, tI4I, contact a of mixer XI in position 4, the winding of XI and the battery.

The electromagnet XI attracts its armature and remains in this position till the release of relay I4 which takes place at the end of the reception of the train of pulses which represents the figure to be received, (here the figure 2);

The circuit of the element which prints the figure of the tens of thousands is closed as follows: a

(Fig. 7) ground, tI32, contact a of mixer XI in position 4, wire I, point II (Fig. 8) the winding. of theelectromagnet 3 and the battery.

At each emission of negative current by the dial of the calling station relay 3 of the recorder (Fig. 4) is released, and accordingly relay I3 of the recorder for charged communications is attracted; on the other hand, relay 3 of the recorder is attracted at each emission of positive current which in turn releases relay I3 of the recorder for charged comunications.

The circuit of the printing element 3 for the figure representing tens f thousands (Fig. 8) is, therefore, established at each emission of negative current and ceases at each emission of positive current. It follows from this that the printing element 3 makes as many steps as there are units in the transmitted figure.

In the example chosen the printing element 3 brings the figure 2 of its wheel which is provided with printing characters, opposite the paper band. 1

Relay I4 of the recorder for charged communications (Fig. 7) is then short-circuited by the contact 1'I3I for a long time, and exhausts its period of delay and falls back, thereby opening at tI4I the attraction circuit of the electromagnet of mixer XI which releases its armature and brings its wipers into position 5, thus disconnecting the printing element 3 and connecting the printing element 4 for the figure which represents thousands.

Contact 133 of electromagnet 3 (Fig. 8) is opened mechanically as soon as the e1ectromag-' net has left its rest position. On the other hand contact H2 is also established mechanically, but only when the electromagnet has left its rest position, and only till its return into this position.

The second figure is received on the printing electromagnet 4 in a manner identical to that described for the first figure, mixer XI of the recorder for charged communications (Fig. 7) being in position instead of 4.

The third, fourth and fifth figures are received by printing elements 56-I (Fig. 8), mixer XI of the recorder for charged communications successively occupying the positions 6, I, 8.

After the reception of the last figure the printing elements of the printing recorder are in the following positions: I

3 in position 2 4 in position 5 5 in position 8 6 in position 8 I in position I 16 After the reception of the last figure mixer XI of the recorder for charged communications (Fig. '7) passes into position 9, the attraction circuit of its electromagnet being open at tI4I.

In this position, printing of the number of the called station is effected. Type wheels carrying printing characters are ShOWn at "II I, H2, H3, H4, H5, H6, H1. Holding contacts which are mechanically held in their position are shown at 32, 42, 52, 62, I2, 92, 33, 43, 53, 63, 13, 93.

The circuit of the electro-hammer of the printing recorder is closed as follows:

Ground, 1584, (Fig. 7), contact a in position 9 of mixer XI, wiper IN of finder CEI, contact IN (Fig. 8), the, winding of the electromagnet s and the battery.

The electromagnet 8 attracts its armature and presses the paper band against the wheels of the printing electromagnets 3 I-56-'I which are equipped with printing characters.

Now the circuit of relay I2 of the recorder for charged communications (Fig. 7) is closed as follows:

Ground, tSI, contact I) of the mixer in position 9, the winding of relay I2, the resistance and the battery.

Relay I2 attracts its armature and at tI2I, it closes the crossing circuit of the electromagnet of mixer XI as follows:

Ground, tI2I, contact 11 of mixer XI in position 9, the circuit-breaker, the winding of XI and the battery.

Mixer XI then brings its wipers into position If), thereby interrupting, at 9, the circuit of the electro-hammer 9 of the printing recorder, which releases its armature.

In position ID the circuit of the electromagnet for advancing the paper band is closed as follows:

Ground, t84, contact a, in position II] of mixer XI,wiper Ab of finder CEI, contact Ab (Fig. 8), the windingof the electromagnet I3 and the battery. I

Electromagnet I3 attracts its armature and advances the paper band. By its contact tI3I it closes the circuit of the relay 2;

Ground, tI3I, the winding of 2 and the battery.

Relay 2 closes a holding circuit as follows:

Ground, til, the winding of 2 and the battery.

Relay 2 then establishes a circuit for the return to rest of printing elements 3-4--5-6-'I via:

Ground, i22, t32, the battery.

T3I, the winding of 3 and Ground, 1:23, 1342, TM, the winding of 4 and the battery.

Ground, t24, 1552, NH, the winding of 5 and the battery.

Ground, H5, 1562, NH, the winding of 9 and the battery.

Ground, t26, t'I2, 1", the winding of I and the battery.

The vibrating elements now return to their rest position; in this position, contacts t32, t42, 1:52, t62 and t'i2 are open, and contacts r33, r43, r53, r63 and T13 are closed. When all the printing elements have returned to their rest positions, relay 2 is short-circuited by means of the following connections:

Ground, tZI, r33, 1'43, r53, r63, r13, T93 and the winding of relay 2.

Then relay 2 falls back, and all the printing elements are ready to receive the number of the calling station.

It has been mentioned that that the Wipers of 17 electromagnet-XI of the mixer have been brought to position II]. In this'position, relay I2'is shortcircuited by the-following circuit:

Ground, tSI, tI22, contact b of mixer XI in position It and relay I2.

Relay I2 then exhausts its period of-ldelay and falls backthereby re-establishing its. contact rI2I.

The circuit of relay 9 is similarly closed in this position as follows:

Ground, t84, contact (1 of XI,. in position. III, the upper winding of Sand thebattery.

Relay 9 closes a holding circuit as follows:

Ground, i134, t92, the lower winding of relay 9, wiper IP of the finder CEI, contact IP' (Fig. 8), the winding of the printing electromagnet for position ID and the battery.

The electromagnet I0 cannot start working because the resistance of the winding of re1ay9 of the recorder for charged communications is too high to permit of its functioning.

The circuit of the combiner Xi is closed as follows:

Ground, rIZI, contact 0 of mixer XI in position II), the circuit-breaker, the winding of XI and the battery.

Electromagnet XI then brings its Wipers into position II.

The recorder for charged communications then begins the search for the calling station. The first phase consistsin the search for the call finder which is in engagement with the calling line. As the designation of this call finder it is sufiicient to indicate the element representing hundreds to-which this'call'finder is connected. The rotation circuit of finder. RC of the recorder for charged communications is closed as follows:

The battery, M23, TI I I, tIIl-I, contact h in position II of mixer XI, the circuit-breaker and the winding of the electromagnet' RC to ground;

The finder RC begins to rotate automatically, and searches for the test plug to which a wire SC, peculiar to each finder, is. connected and which indicates to it that the wiper of the connection circuit is in' engagement with the r..- corder.

The rotation circuit of electromagnet RC is opened as soon as wiper B of switch RC has reached this test plug. Then relay H of therecorderfor charged communications (Fig. 7) be gins to operate by means of the following connections:

(Fig. 6) the secondary ofthe transformer, rectifier RDI or RDZ in the same direction as the current, point: 23: (Fig. 4 75321,, rI-i-I, wiper SI of the finder of the recorder, contactSI of the bank (Fig. 3), the wiper and bank S of the finder of the connection circuit, wire sc (Fig; '7), the bank andwiper b'of'fi'nder RC, contact-f of mixer XI in position I I, H05, the winding of relay I I, TIM, tI3, wiper S of the finder of recorder CE, the bank 8 (Fig. 4), 15! I6, rectifier R1)! in the same direction as the current, tIZ, point 24 (Fig. 6), rectifiers' RD3- or RD4 in the same direction as the current, and the secondary or transformer TF I.

Relay II" opens the rotation circuit of finder CE at H l I. At rI I2, it closes the attraction circuit of relay I! by means of the' fo'llowing connections-i Ground, t8I; tI contact I) of the mixer in position I I, the winding of relay 5 I, the resistance and'the battery. I T

Relay" I2 closes a holding circuit by means of contact H22. Italso closes the circuit of the electromagnet Of mixer XI by means of the following connections:

Ground, tI2 I, contact'z' inposition I I of XI, the circuit-breaker, the winding of XI and; the bat;-. tery.

The electromagnet of XI then brings its wipers into position I2.

Relay I2 is then short-circuited. by. contactb of mixer XI in position I2,. and. falls. back;

Relay II, the circuitof whichis open (atcontact III of the mixer XI), falls back in its? turn.

. The rotation circuit of finder:R.A..is.then closed via:

The battery, rI I I, tIOI.,,contact hof mixer XI in position I2, the wiper. and .bank 0 of finder R.C., the circuit-breaker the winding of R-.A.',.and the battery. The finder RA. beginsto rotate automatically and searches for the test-plugto. which. a wire S peculiar to each subscriber is connectedjand which indicates to it that wiper S of the connection circuit is in engagement with the recorder and that wiper S of the call finder is in engagement with the calling line. The rotation: circuit of the. electromagnet R.A, is openedas soon as wiper a (orb, c, d; e or 1 according to'the: element representing. thehundredto which thesubscriber belongs) reaches this test-plug. The cir cuit of relay II of'the recorderfor charged communications (Fig. 7) is then closed asv fol-lows:

(Fig. 6) the secondary of the transformer, rectifiers RDI or RD2 in the same direction as. the current, point 23' (Fig. 4),.t'l2f, TI I I, Wiper SI of the finder of the recorder, contact :SI of the bank (Fig. 3), thewiper andbankiS of theLfinder of the connection circuit, 75024 wiper Sand: bank 8 of. the call finder, point Sa' (Fig. '7), the; bank and wiper A of finder RA, bankA and wiper A of finder RC, contact of mixer: XI? in position I2, H05 the winding of 'relay- I I', N21,. H03, wiper S of finder C.E., bankiS (Fig. 4) tII5, rectifier RDI- in the same direction as the: current, 152, point 24 (Fig. 6),.rectifiers RD3? or RDA in the same direction as thecurrent,.andthe'secondary of TFI.

Re'lay'l I begins to operate, and at rII I it opens the rotation circuit of the electromagnetofcXI'.

The circuit-ofthe electromagnet of mixer: 'X I is closed as follows:

Ground, tBl, tI I2, contact 2' of mixer XI in position I2, the circuit breaker, the winding of the electromagnet of XI: and the battery.

The electromagnet brings. the Wipers of mixer XI into position I2. In this position relay. I5 (Fig. 7) which had. already begun to operat by means of the following connections:

t8l, the winding of relay I5, contact 2' in position-s of mixer XI, the resistance Kiandthe b'attery; andwhich had closeda holding circuit by means of contact if! 52, closes (by its contact tI5 I) the circuit ofthe electromagnet of mixer XI as follows:

Ground, contact 9 of mixer. XI in position I3, H84, the Winding of XI andthe battery.

' But relay I 5 is short-circuited by means of the following connections:

Ground, contact h of the mixer XI in position I3, wiper a in the rest position of switch X2, H53, the winding of relay I5, tBI and ground.

Relay [5 then falls-back, thereby opening at tI5I the circuit of the electromagnet of the mixer XI which brings its wipers into position I4.

Zihe circuit of the reciprocating members of relays I6 and is established "as follows:

Grou nd, contact- 17 of'.mixer=':XI in position I4, 

